1. Field of the Invention
The present invention relates to a touch panel display device, and more particularly, to a touch panel display device capable of decreasing power consumption and manufacturing costs by reducing the number of image sensors and infrared light emitting diodes, and capable of improving touch sensitivity even when a screen has a large scale.
2. Discussion of the Related Art
With the wide use of computers for data processing, users increasingly need to input more data to data processors, such as workstations, personal computers, etc., or need data processing (e.g., data conversion) using data processors. Diverse application programs can be applied to the recent developed data processors, and complex data processing can be achieved by combination of the application programs.
However, it is very difficult to handle the data processors. Specifically, persons having little knowledge about computers have considerable difficulty in handling data displayed on a display device. In this regard, the demand for an improved device, enabling even persons who have little knowledge about computers to easily handle the displayed data, has increased.
Generally, in order to handle the data displayed on the display device, an operator needs to input a command for processing the data by use of a keyboard or mouse, or needs to input a command to select an icon (representation of a program, file, directory or device) displayed on the display device by use of a keyboard or mouse in order to carry out a desired function. However, because it is troublesome to input a desired command using a keyboard or mouse and an icon, a user having little knowledge about computers may have difficulty in even using a keyboard or mouse.
In this regard, so as for even a user having little knowledge about computers to easily handle an apparatus such as a data processor, development of a display device having a touch panel capable of processing data by only finger touch has been required.
In general, a touch panel is one of various types of forming an interface between information and communication equipment using a display device and a user. The touch panel serves as an input device that enables a user to input desired information to the equipment by directly touching a screen with a finger or a touch pen.
There are two representative types of touch panels, one of which is a resistive type touch panel, and the other of which is an infrared touch panel.
A resistive type touch panel uses a conductive film, and is constituted such that chemicals are coated between a glass and a thin film, and a thin metal plate is attached to side surfaces in X and Y axis directions. If electric power is supplied to such a panel, a predetermined resistance is generated. If a certain portion of the panel is touched with a finger or other objects, the chemicals react to the touch, and the resistance is changed in a moment. In the metal plate provided on the side surfaces, position coordinates of the portion touched with the object are derived from the change of the resistance.
An infrared touch panel includes an infrared generating device for radiating infrared light in a cross stripe shape on a display panel, and a sensing device to sense the infrared light generated from the infrared generating device. In such an infrared touch panel, if a certain portion of the display panel is touched with a finger or other objects, the infrared light passing through the touched portion is interrupted. The sensing device such as an image sensor senses the interruption of the infrared light, and thereby position information of the touched portion is derived.
A user does not necessarily touch only the center portion of the touch panel, but touches any portion of the touch panel. In order to increase accuracy of detecting a touched position on the whole region of the touch panel, a plurality of infrared generating devices are required, and accordingly a plurality of infrared sensing devices are also required.
An example of such a conventional touch panel display device is disclosed in U.S. Pat. No. 6,972,401 (issued on Dec. 6, 2005).
FIG. 1 is a plan view illustrating a conventional touch panel display device, and FIG. 2 is a perspective view illustrating infrared light emitting diodes of the conventional touch panel display device.
Referring to FIGS. 1 and 2, a conventional touch panel display device 1 includes a liquid crystal display module having a back light unit (not shown) and a display panel 58, and touch sensing parts 68 provided above the liquid crystal display module.
The display panel 58 of the liquid crystal display module displays an image, and the back light unit of the liquid crystal display module supplies light to the display panel 58. The illustration of the back light unit is omitted in FIGS. 1 and 2.
The back light unit may include a plurality of light sources (not shown) to irradiate light to the display panel 58, a bottom cover (not shown) which is mounted with the light sources and an optical member for guiding the light emitted from the light sources to the display panel 58, a diffusion plate (not shown) to diffuse the light emitted from the light sources to the whole surface of the display panel 58, and a plurality of optical sheets (not shown) provided above the diffusion plate in order to guide the diffused light radiated from the diffusion plate in a direction perpendicular to the display panel 58.
Depending on the arrangement structure of the light sources for supplying light to the display panel 58, the back light unit is classified as an edge light type and a direct type. The back light unit as described above is a direct type back light unit. An edge light type back light unit is structured such that the light sources are arranged on the lower side surface of the display panel 58. Therefore, the edge light type back light unit is provided with a light guide plate to guide the light emitted from the light sources to the display panel 58.
In the conventional touch panel display device 1, the touch sensing parts 68 for sensing the infrared light are disposed at upper corners of the display panel 58, frames 64 are provided to be extended along the edges of the display panel 58, and a plurality of infrared light emitting diodes (IR-LEDs) 66a are provided in the frames 64. The IR-LEDs 66a emit infrared light to a surface 60 of the display panel 58. More particularly, the IR-LEDs 66a are arranged on a substrate 66b, and are mounted in the frames 64.
The conventional touch panel display device 1 is constituted such that a user can observe an image displayed on the display panel 58 and can touch a user's desired portion of the panel, to thereby input information. To achieve this, the touch sensing parts 68 for detecting the position touched by a user are provided at the upper corners of the display panel 58.
The infrared light generated from the IR-LEDs 66a shown in FIG. 2 is irradiated to the surface 60 of the display panel 58 via a light guide plate 66c provided at a light output surface of the frame 64. The light guide plate 66c serves to expand an irradiation range of the infrared light emitted from the IR-LEDs 66a. The light guide plate 66c may be generally configured as a film or lens.
As shown in FIGS. 2 and 3, the infrared light emitted from the IR-LEDs 66a passes through the light guide plate 66c, so that the irradiation range of the infrared light is expanded. Then, the infrared light is irradiated to the surface 60 of the display panel 58. A reference numeral 72 in FIG. 3 denotes that the irradiation range of the infrared light is expanded by the light guide plate 66c. 
By the above constitution, the infrared light generated from the IR-LEDs 66a is irradiated to the surface 60 of the display panel 58. If a user observes an image displayed on the display panel 58 and touches a certain portion at which user's desired information is displayed, the infrared light incident on the touch sensing parts 68 including image sensors is interrupted.
The image sensors included in the touch sensing parts 68 are provided with infrared pass filters (IR-Pass Filters) to interrupt visible light and sense infrared light. As shown in FIG. 4, when a user does not touch the panel, because the infrared light is incident on the image sensors, a white image is inputted.
If a user touches the touch panel, the infrared light is interrupted by a user's finger, and thus a black image is inputted to the image sensors.
The touch panel display device 1 using infrared light analyzes an image of the object touching the panel by generally using two or more image sensors. Thereafter, an angle of the image and coordinates are derived using a triangulation method, and a portion of the display panel 58 corresponding to the coordinates, i.e., a portion of the display panel 58 touched by a user is detected. As a result, a touched position is determined.
The conventional touch panel display device 1 as constituted above includes a plurality of IR-LEDs 66a in order to accurately detect the position touched by a user and improve touch sensitivity.
Thus, the above conventional touch panel display device 1 has problems of high power consumption and high manufacturing costs. Moreover, the number of IR-LEDs 66a is more increased as the display panel of a larger scale is produced. Accordingly, the power consumption and manufacturing costs are considerably increased.